Door knob



FIG. 1 is a right perspective view of a door knob showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a left elevation view thereof; and,

FIG. 7 is right elevation view thereof.

The dashed lines in FIGS. 1-7 show rear portions of the door knob and a cylinder lock which are included for environmental purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a door knob, as shown and described. 